Sometime over the weekend, you might be invited to play a guessing game we play around here. What was the groundbreaking political story of the year? You could be forgiven for saying the election, of course, but that would be obvious, and we do have elections every four years. But elections have consequences and so do Supreme Court decisions.

We begin by looking at some of the biggest political news of the year with Newsweek/Daily Beast correspondent Michael Tomasky. Thanks for coming in.

MICHAEL TOMASKY: It's nice to be with you, Jacki.

LYDEN: So, of course, one of the biggest things of the year was last summer's Supreme Court decision in which the Obamacare mandate, as we now all call it, was upheld. Let's hear a clip from the president speaking on that day.

PRESIDENT BARACK OBAMA: Today's decision was a victory for people all over this country whose lives will be more secure because of this law and the Supreme Court's decision to uphold it.

LYDEN: This was absolutely seismic. Now, we're going to see more of the implementation between now and 2014, right?

TOMASKY: And we'll certainly see more challenges. Many Republican governors have decided not to opt in to the state exchanges or not to set up the state exchanges, which raises some questions about how the whole thing will work. So the health care law is not yet out of the woods, even though the Supreme Court, to most people's surprise, said that it was OK constitutionally.

LYDEN: Let's take a look at Scott Walker, the first-term Wisconsin governor who beat back a campaign to oust him from office. Scott Walker's decision to basically bust public sector unions led to just a convulsion of demonstrations in Madison. Let's listen to Governor Walker.

GOVERNOR SCOTT WALKER: Tomorrow is the day after the election. And tomorrow, we are now no longer opponents. Tomorrow, we are one as Wisconsinites. So together...

LYDEN: Are we one in Wisconsin or any other state, Michael Tomasky?

TOMASKY: No. No state that I can think of are we one. You know, Walker survived because a lot of people who opposed what he did thought that even so, it was a little much to recall a governor, that he had won fair and square and that he was the governor and that that was maybe a little bit of an overreaction. I was most struck by that poll after the vote that I think 17 percent of people who voted to retain him opposed his move against the unions.

The future ramification, I think, is for unions and for public employee unions, they did put up a pretty strong fight. They didn't have a great alternative candidate, but they'll have to work harder if they try something like that again, but they'll have to pursue other avenues such as in Ohio where voters voted down Governor Kasich's similar move against unions.

LYDEN: Michael Tomasky, last year saw a number of horrific shootings. Aurora, Colorado, is just leaping to mind right now: 12 dead, scores injured. And, of course, the Newtown mass killing. What effect do you think these shootings are likely to have on the gun control debate?

TOMASKY: I think that they will and have already increased the percentages of some Americans who want some kind of action, want some kind of limitations imposed on assault weapons, perhaps on ammunition, background checks, those kinds of steps. I think Newtown in particular, obviously because of just an unbelievably ghastly nature of that really, really hit people and hit people across the board, whether they're Democratic or independent or Republican.

LYDEN: What about gay marriage? Would you say that 2012 was the year that gay marriage turned the corner? Our polls show that most Americans - the vast majority, really - support it.

TOMASKY: Absolutely. I think that was a real watershed. And I'd say even more broadly that the election itself represented a real cultural shift in the country. Almost as if a switch was flipped. A lot of people assume Democrats and Republicans alike that 2008 was a bit of a one-off and that Obama couldn't really reassemble that coalition again in 2012. But he did, and it made itself felt not only in Obama's win, but in measures like the same-sex marriage measures in Maryland, where I live, and two other states and in those marijuana legalization referenda in Colorado and Washington.

LYDEN: Would you say, when you look back at this year, and where we are now on the precipice of the fiscal cliff, that the country worked things out or at least voted on social issues. But that when it comes to the actual business and machinations and government, particularly at the federal level, we're really stuck.

TOMASKY: I would say that's true. I think the conservative element of America constitutes, as far as we can see, 30 to 35 percent of the population. And that 30 or 35 percent is frankly overrepresented in the halls of Congress where there are very, very few moderate Republicans. And most of the Republicans in the House and Senate are terrified of having a primary challenge from their right. And that governs a lot of their behavior here in this fiscal cliff negotiation. And it will govern a lot of their behavior as we go forward in 2013 and try to deal with gun legislation potentially or immigration legislation.

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